According to technological advancements, the use of advanced driver assistance systems (ADASs) for assisting a driver has increased. Examples of the ADAS include a forward collision warning system (FCWS) for warning a forward collision, and a lane departure warning system (LDWS) for warning a lane deviation. However, an unnecessary warning may be raised if the ADAS is unable to recognize a state of a driver, is thereby causing the driver inconvenience. In other words, it needs to be determined whether a lane change is intended by the driver or is caused by careless driving. Meanwhile, if abnormal driving, such as a lane deviation, occurs during high-speed driving, a time for reacting to a warning is very short, and thus an apparatus for sensing carelessness of the driver early and warning the driver is required.